未定义对 `JNI_CreateJavaVM' linux 的引用

2022-01-25 00:00:00 c++ java-native-interface

我正在尝试熟悉 JNI API，但无法编译示例 C++ 程序.

I'm trying to get familiar with the JNI API but can't get a sample c++ program to compile.

这是我用来编译的命令，下面是我要编译的程序.我得到的错误是:

Here is the command I'm using to compile and below that is the program I'm trying to compile. The error I get is:

/tmp/cczyqqyL.o: In function `main':
/home/nc/Desktop/jni/simple/ctojava/callJava.cpp:16: undefined reference to `JNI_CreateJavaVM'

编译:

g++ -g -I/usr/lib/jvm/java-7-oracle/include/ -I/usr/lib/jvm/java-7-oracle/include/linux/ -L/usr/bin/java -L/usr/lib/jvm/java-7-oracle/jre/lib/amd64/server/ -ljvm callJava.cpp

C++:

#include <jni.h> /* where everything is defined */

int main(){
    JavaVM *jvm; /* denotes a Java VM */
    JNIEnv *env; /* pointer to native method interface */

   JavaVMInitArgs vm_args;
   JavaVMOption options[1];
   options[0].optionString = "-Djava.class.path=/home/nc/Desktop/jni/simple/ctojava/";
   vm_args.version = JNI_VERSION_1_6;
   vm_args.options = options;
   vm_args.nOptions = 1;
   vm_args.ignoreUnrecognized = JNI_FALSE;

   /* Create the Java VM */
   int res = JNI_CreateJavaVM(&jvm, (void **)&env, &vm_args); // this is what it can't find

   /* invoke the Main.test method using the JNI */
   jclass cls = env->FindClass("Hello");
   jmethodID mid = env->GetStaticMethodID(cls, "staticInt", "(I)I");
   env->CallStaticVoidMethod(cls, mid,10);

   /* We are done. */
   jvm->DestroyJavaVM();
}

我已经搜索了这个问题并尝试了我找到的所有解决方案，但我仍然遇到同样的错误......非常感谢任何帮助！

I've searched for this issue and tried every solution I've found but still I get the same error... Any help is greatly appreciated!

Joni 在下面的回答有效(取决于您的编译器).万一其他人发现:运行编译输出时不要忘记 LD_LIBRARY_PATH=_path_to_your_libjvm.so_ 否则它将无法在运行时找到该库.

Joni's answer below works (depending on your compiler). In case someone else finds this: when running the compiled output don't forget LD_LIBRARY_PATH=_path_to_your_libjvm.so_ or it will not be able to find that lib at runtime.

LD_LIBRARY_PATH=/usr/lib/jvm/java-7-oracle/jre/lib/amd64/server ./a.out

推荐答案

GCC 查找符号的方式最近发生了变化:现在要链接的单元严格从左到右处理，并且对库的引用(-lYourLibrary) 如果命令行左侧没有需要它们，则会被静默忽略.

The way GCC finds symbols was changed fairly recently: now the units to be linked are processed strictly from left to right, and references to libraries (-lYourLibrary) are silently ignored if nothing to their left in the command line needs them.

要解决这个问题，请将 -ljvm 移到使用它的编译单元之后，例如移到命令行的最后:

To fix this, move -ljvm after the compilation units that use it, for example to the very end of the command line:

g++ -g -I/usr/lib/jvm/java-7-oracle/include/ -I/usr/lib/jvm/java-7-oracle/include/linux/ 
-L/usr/bin/java -L/usr/lib/jvm/java-7-oracle/jre/lib/amd64/server/ callJava.cpp -ljvm

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